Source : Webster's Revised Unabridged Dictionary (1913)

Rosin \Ros"in\, n. [A variant of resin.]
   The hard, amber-colored resin left after distilling off the
   volatile oil of turpentine; colophony.

   {Rosin oil}, an oil obtained from the resin of the pine tree,
      -- used by painters and for lubricating machinery, etc.

Rosin \Ros"in\, v. t.
   To rub with rosin, as musicians rub the bow of a violin.

         Or with the rosined bow torment the string. --Gay.

Source : WordNet®

rosin
     n : any of a class of solid or semisolid viscous substances
         obtained either as exudations from certain plants or
         prepared by polymerization of simple molecules [syn: {resin}]
     v : rub rosin onto; "rosin the violin bow"